University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln
Proceedings of the 2nd Vertebrate Pest Control
Conference (1964)
Vertebrate Pest Conference Proceedings collection
3-6-1964
RABBIT CONTROL
Warren V. Johnson
California Department of Agriculture
Follow this and additional works at: http://digitalcommons.unl.edu/vpc2
Part of the Environmental Health and Protection Commons
Johnson, Warren V., "RABBIT CONTROL" (1964). Proceedings of the 2nd Vertebrate Pest Control Conference (1964). Paper 15.
http://digitalcommons.unl.edu/vpc2/15
This Article is brought to you for free and open access by the Vertebrate Pest Conference Proceedings collection at DigitalCommons@University of
Nebraska - Lincoln. It has been accepted for inclusion in Proceedings of the 2nd Vertebrate Pest Control Conference (1964) by an authorized
administrator of DigitalCommons@University of Nebraska - Lincoln.
RABBIT CONTROL
Warren V. Johnson Weed and Vertebrate Pest Control
C a l i f o r n i a Department of Agriculture, Fresno, C a l i f o r n i a
Common C a l i f o r n i a rabbits comprise two major genera. One, the genus
S y l v i l a g u s , or true r a b b i t , is represented by the cottontail and brush rabbits.
B a s i c a l l y , the members of t h i s genus l i v e in dense cover, stone p i l e s ,
thickets, under b u i l d i n g s , or in burrows. At b i r t h the young are covered w i t h
extremely short h a i r , t h e i r eyes closed, and they remain so for about 10 days.
They remain in the nest u n t i l f u l l y furred and are a b l e to care for themselves.
These rabbits are classed as game and may be taken during an open season as
declared by the C a l i f o r n i a F i s h and Game Commission. In a d d i t i o n to an open
hunting season on these rabbits, the C a l i f o r n i a F i s h and Game Code authorize
t h e i r taking by land owners or tenants or persons authorized in w r i t i n g by
them where damage to crops or forage is being experienced. Other control methods
for these species include exclusion and repellents. These methods w i l l be
discussed in more d e t a i l later in t h i s report.
The second of the two major genera is the genus Lepus, or hares. These are
erroneously c a l l e d the jack rabbits and snow shoe r a b b i t s . The common jack
ra bb i t, Lepus californicus, is the most f a m i l i a r one throughout C a l i f o r n i a and
portions of some of the other western states. Because of their s i z e and
abundance, they are by far the most destructive - so emphasis w i l l be placed on
t h i s species throughout the balance of t h i s report. U n l i k e the cotton t a i l s
or brush rabbits, jack rabbits occupy the open or semi-open lowlands, f o o t h i l l
and desert areas as w e l l as the humid coastal region - ranging from below sea
level in Death V a l l e y to well over 12,000 ft. elevation. Females may produce
from 3 to 8 per l i t t e r and as many as 3 l i t t e r s a year -w i t h an annual average
of 13 to 14 young per female. The annual rate of reproduction may vary from
year to year, apparently due to e x i s t i n g environmental conditions. In most of
C a l i f o r n i a the peak of the breeding season occurs d u r i n g the months of A p r i l
and May. T h i s is an interesting contrast to the jack rabbits of the same species
of the southern desert areas and Arizona where they apparently have two peak
breeding seasons d u r i n g the year --one in the winter and one in the summer which
are correlated w i t h the rainy season of that country. Young jack rabbits are
f u l l y haired, have their eyes open at b i r t h and w i t h i n a few days can s h i f t for
themselves.
The d i e t of the jack rabbit consists mostly of a v a i l a b l e vegetation. T h i s
includes a wide variety of herbs, shrubs, and succulent grasses. Food
consumption studies have indicated that about 12 jack rabbits w i l l consume the
same amount of forage as 1 mature ewe, or that 60 rabbits w i l l consume about
the equivalent of a 1,000 lb. range cow. Because of frequent feedings on
seedling p l a n t s of cultivated crops as well as g r a i n , bark of young trees, and
young grapevines, control measures are often necessary. Also, in recent years,
h i g h populations of rabbits in the v i c i n i t y of airports have brought about
potential hazards to aircraft and a reduction of the population in these areas
has been necessary.
The methods of rabbit control are several - i n c l u d i n g the encouragement of
natural enemies, shooting, trapping, exclusion, repellents, and poisoning.
90
Natural enemies of the rabbit include the large hawks and owls, eagles,
coyotes, w i l d c a t s , foxes, weasels, dogs and cats. These natural enemies are
seldom ever numerous enough to control rabbits. Even though other methods must
often be used, these natural enemies should not be i n d i s c r i m i n a t e l y
slaughtered. Under certain c o n d i t i o n s , shooting has proven effective as a
means of preventing rabbit damage. Systematic p a t r o l l i n g in the e a r l y morning
and l a te evening may effectively reduce the population and suppress the damage
in a l o c a l i z e d area. Organized r a b b i t hunts have proven satisfactory in reducing the population over local areas. T h i s type of control is usually more
effective in open t e r r a i n rather than c u l t i v a t e d f i e l d s , orchards, or vineyards;
recently there has been reluctance by farmers and sportsmens clubs to organize
these hunts due to the responsibility or l i a b i l i t y of injury or damage involved.
Trapping with the box or s i m i l a r type trap or snaring is often effective,
but t h i s is a slow method of control for cottontails. It is not a successful
method for c o n t r o l l i n g jack rabbits because of t h e i r reluctance to enter a trap
or dark enclosure. Trapping in conjunction w i t h rabbit d r i v e s , where a large
t e r r i t o r y is surrounded by men and the rabbits d r i v e n into a corral, may be
considered a method of trapping that has been successful. Another s i m i l a r
type of trapping operation is the construction of a small corral along a r a b b i t t i g h t fence surrounding a protected f ield . Another short s t r i p of fence is
constructed at a diagonal to the m a i n fence, funneli n g the rabbits to a one-way
gate into the corral. D a i l y inspection of the corral can then be made - and
trapped animals disposed of.
E x c l u s i o n is most often accomplished by the construction of rabbit-proof
fences and gates around the area to be protected. Woven w i r e or poultry
netting of a mesh not greater than one and one-half inches, 30 to 36 inches
h i g h , w i t h the bottom 6 inches turned outward and buried at least 6 inches in
the ground, should exclude a l l rabbits from the area to be protected. Where it
has not been practical to erect gates, dogs have been chained at the openings,
provided w i t h water and some food, and have served a useful purpose in keeping
rabbits from entering. Exclusion by fencing is d e s i r a b l e for s m a l l areas, but
most often impractical and expensive for larger acreages of farm land. The use
of i n d i v i d u a l mechanical protectors to guard the trunks of young trees or vines
may a l so be considered a form of exclusion. Among the best of these mechanical
contrivances are cylinders made from woven wire netting. Poultry netting of I
inch mesh, 20 guage galvanized w i r e 18 inches wide should be used. T h is is cut
into s t r i p s 12 to 18 inches wide and formed into cylinders around the trees.
To afford adequate protection, these c y l i n d e r s should be braced away from the
trunk to prevent rabbits from pressing them against the trees and gnawing
through them.
Types of tree protectors commercially a v a i l a b l e i n c l u d e aluminum and
nylon mesh wrapping and one made of treated jute cardboard. Aluminum f o i l ,
or even ordinary sacking, has been wrapped and t i e d around trees w i t h effective results.
Various chemical repellents are offered as a means of reducing or preventing rabbit damage to trees, vines, or farm and garden crops. The purpose of
a rabbit repellent is to make the protected plants less desirable by treating
w i t h a material distasteful to the rabbit. Also, a satisfactory rep e l l e n t must
be non-injurious to trees or plants, when applied at any time of the year.
91
In the past there has been a considerable variety of repellents recommended in the form of paints, smears or sprays. Many of these afford o n l y
temporary protection and must be renewed too often to warrant t h e i r use. Other
materials that would last have caused injurious effects to the treated plants.
Some chemical substances that have provided a certain amount of protection and
yet were harmless to plants are lime-sulphur, copper carbonate, and asphalt
emulsions. Concoctions u s i n g these m a t e r i a l s had to be mixed by the
applicator or farmer and have presently been replaced w i t h various commercial
preparations that are e a s i l y mixed and probably more effective. Repellents
are applied either during the winter dormant season or summer growing season
and recommendations vary accordingly. The following are some of the
commercially a v a i l a b l e repellents: Arasan 75, Arasan 42-S, Ringwood
Repellent, Improved Z.I.P., and Pennco Animal Repellent. These should be used
according to the manufacturer’s recommendation - which should be c a r e f u l l y
checked as to the season for use as brush or spray recommendations may differ.
One other material often used as a repellent to protect young trees from
rabbits is a strychnine poison wash. T h i s is a mixture of strychnine s u l phate,
laundry starch, g l y c e r i n and water. It should not be a p p l i e d , however, where
domestic animals are present.
One precaution which must be taken when u s i n g repellents is that no
a p p l i c a t i o n should be made to plants after the e d i b l e portion of the plant
has started to form.
The last of the methods of control to be discussed is poisoning. The use
of toxic grain b a i t s is perhaps the most practical and economical methods of
control where large numbers of rabbits are present or large areas are to be
protected. Poisoning, as a means of control, should o n l y be used if the local
situation is such that humans, domestic animals, and other forms of w i l d l i f e
w i l l not be endangered.
Methods of exposing b a i t for rabbit control vary considerably, depending
on the type of area to be treated. If b a i t s are to be exposed on open range,
stock-proof corrals may be used. These should be at least 20 ft. square w i t h
the bottom w i r e not closer than 10 inches to the ground. T h i s w i l l l e t the
rabbits enter the corral but keep livestock or larger a n i m a l s away from the
exposed baits. Where rabbits are invading green f i e l d s from surrounding
desert or dry areas, s m a l l handfuls of b a i t should be placed in t r a i l s 100
yards or more from the f i e l d for better b a i t acceptance. In areas where
t r a i l s are not readily available baits may be distributed in small handfuls in
rows about 15 ft. apart and from 5 to 10 ft. in the row. Drags in plowed land
w i l l often create a runway in which baits may be exposed. In the d r i e r areas
the a d d i t i o n of extra water to the bait, to the point where it can be squeezed
from the bait, has also proven effective as a means of improving b a i t
acceptance. Since the rabbits feed mostly in the evening and at n i g h t , a l l
b a i t exposure should be done in the late afternoon or early evening for best
results.
Prebaiting for 3 or 4 days, or if necessary, longer, is one of the
essentials of a successful rabbit control program. Replenishing of prebaits in
the same spots as the i n i t i a l prebaiting is helpful in obtaining satisfactory
bait acceptance. Toxic baits should then be placed at the locations where
prebait was best accepted.
92
One of the most commonly used formulas for jack rabbit b a i t has been
rolled barley with o i l of anise. This is used f i r s t as a prebait and then as the
toxic bait when treated w i t h .2% strychnine a l k a l o i d .
Other methods of bait preparation include the use of root vegetable and
f r u i t ba its ; a l f a l f a leaves; oats; m i l o , barley or sorghum heads; and s a l t
blocks or s a l t l i c k s . The use of most of these methods is s u i t a b l e only for
protection of a l i m i t e d acreage and are not too practical for the treatment of
larger areas. (Formulas for the use of these baits w i l l be included in the
proceedings - so they w i l l not be covered in detail at t h i s time.)
Strychnine treated water has been exposed in desert areas with good res u l t s , however, t h i s method is discouraged as there is no selectivity and it is
extremely hazardous to other forms of w i l d l i f e or domestic animals that may be
present in the area.
Recently the Fresno County Agricultural Commissioner's Office conducted
some t r i a l s u s i n g a½% strychnine bait. Bait preference plots in the t r i a l area
indicated l i g h t l y rolled oat groats to be preferred over rolled barley.
Prebaiting was carried on for 4 days to establish good bait acceptance.
S l i g h t l y scattered p i l e s of toxic baits were then placed at the same locations
where prebait was accepted. B a i t sizes for the 1 ½ % strychnine baits were 3
grams, or . 1 1 of an ounce, compared to approximately 56 grams or 2 ounces
generally used in the .2% strychnine rolled barley baits. Their evaluation of
these t r i a l s for t h i s localized area indicated an estimated 90% reduction of
the rabbit population and crop depredations were stopped immediately after
treatment. Most of the dead rabbits were found w i t h i n 100 ft. of bait placement and inspection of the stomach contents of the individual dead rabbits
revealed that 3 to 5 kernels of the toxic bait had been consumed.
Anticoagulant treated baits have been used with reports of varying degrees
of success - and for the most part, unsatisfactory. Some rabbits w i l l be
eliminated, but due to the large quantity of bait consumed, t h i s procedure is
not considered economically feasible - unless used to protect high priced
specialty crops in areas where other types of baits cannot be used.
In moderate numbers jack rabbits are beneficial because of their value as
a game animal, for their s k i n s , and for food. When rabbits compete w i t h
livestock for feed or cause damage to trees, vines, or f i e l d crops, economic
control becomes necessary. By economic control we mean the reduction of the
rabbit population in a given area, to a point where crop damage is alleviated.
Control directed toward specific rabbit problems is the most effective and is
advocated only where considered necessary. Problems involving control measures
vary for different locations and situations, and should be worked out to conform with the local conditions. The changing environment brought about by
bringing new lands under i r r i g a t i o n and cultivation, the introduction of des i r a b l e food or forage crops into these areas, and overgrazing of rangelands
encouraging growth of better rabbit forage are some factors which present
problems in control procedures and techniques.
Reports on new or improved methods of preventing rabbit damage and rabbit
control are actually o n l y progress reports - as the research job of jack rabbit
control is never done.
93
FORMULAS FOR USE IN JACK RABBIT CONTROL
POISON WASH FOR TREES:
Strychnine sulfate----------------Laundry (gloss) starch- ----------Glycerine----- -- - ---------------Water- ----------------------- ---
1 ounce
8 ounces
6 ounces
3 ½ quarts
Prepare the laundry starch by m i x i n g cold and then b o i l i n g in one p i n t of
water. D i s s o l v e the strychnine in the remaining water by b o i l i n g . Add to
paste and glycerine. Cool and paint on trunks of trees. Do not admit
domestic a n i m a l s to orchards where t h i s poison wash has been a p p l i e d .
It may be necessary to apply repellent frequently in order to cover
new growth.
Do not treat vegetables after e d i b l e portion has started to form on
beans, cabbage, l e t t u c e , etc., as the repellent may be enclosed.
POISON BARLEY WITH ANISE:
This formula has proven q u i t e effective in many cases, possibly
t h i s may be due to the e l i m i n a t i o n of the starch from the formula or
the addition of anise o i l to the bait. The barley used has been termed
l i g h t l y rolled or c r i m p rolled barley, but regul a r rolled barley used
for horse feed w i l l do if other is not available.
The pre-bait is prepared as follows:
100 lbs. -- Rolled barley
2½ oz. ---- Table s a l t
3 drops
O i l anise
3 quarts
Hot water
Dye (water s o l ub le ) *
Add s a l t to water and d i s s o l v e .
Add anise.
Pour over g r a i n and m i x .
Poison bait:
100 lbs. --- Rolled barley
2 ½ oz. ---- Table s a l t
3 drops ---- O i l a n i s e
3 quarts -- B o i l i n g water
5 oz. --- — Strychnine a l k a l o i d
Dye (water soluble)*
Slowly add a cup of hot water to the strychnine and s t i r u n t i l a t h i c k
paste is formed. (More hot water can be added if necessary.) Pour into
3 quarts of b o i l i n g water. S t i r thoroughly w h i l e pouring in the
strychnine. Add the table s a l t and s t i r u n t i l dissolved. Add o i l of
anise and s t i r . The anise may form a t h i n scum. Pour over g r a i n and
mix. If the above procedure is not followed, the strychnine is apt to
foam and float in the b o i l i n g water,
(continued)
94
(continued — POISON BARLEY WITH ANISE)
The above formulas are for use in a power mixer and eliminate drying
of the b a i t . Additional water w i l l be necessary if the material is hand
mixed.
(*) It is advisable to add some water soluble dye to both the prebait and
bait to serve as a deterrent to birds and to a i d in the identification
of the prepared b a i t .
ROOT VEGETABLE AND FRUIT BAITS:
Chopped baits of any of the root vegetables, including carrots, sweet
potatoes and parsnips or c u l l hard f r u i t as green pears or c u l l apples
form a very satisfactory b a i t . The bait should be chopped into small
squares one-fourth of an inch ( ¼ inch) square, or less, washed and well
drained and then sprinkled or sifted w i t h powdered a l k a l o i d strychnine in
proportions of 1/2 of an ounce strychnine with one-fourth of that quantity
of common table s a l t ground together in a mortar, to two gallons of cut
bait. The bait should be constantly stirred at the time the strychnine is
sprinkled over it to insure uniform d i s t r i b u t i o n . During the dry season,
melons have often proven effective. Watermelons cut into portions, or left
almost whole with a s l i c e out of one side, can have the cut portion rubbed
w i t h powdered a l k a l o i d of strychnine, or incisions made, into which
crystals of strychnine sulfate are introduced.
ALFALFA LEAVES:
Dissolve one ounce of strychnine sulfate in two gallons of hot water
and sprinkle over ten pounds of dry alfalfa leaves. Mix the leaves
thoroughly u n t i l a l l the moisture is absorbed. The poisoned leaves should
be distributed in small handfuls in l i n e s a few feet apart across portions
of the f i e l d where observations show the rabbits to be feeding. In
locations where a l f a l f a is not raised, g r a i n heads may be substituted.
POISON OATS:
Mix thoroughly one ounce powdered strychnine a l k a l o i d and one ounce
baking soda. Dissolve one heaping tablespoon of laundry starch in a
l i t t l e cold water, and add one quart b o i l i n g water. Boil and s t i r until
thin, clear paste is formed. Slowly s i f t mixture of strychnine and soda
into starch paste, s t i r r i n g constantly u n t i l it becomes a smooth, creamy
mass. Add one-eighth ounce of saccharin and 1/2 ounce glycerine and s t i r
thoroughly. Pour t h i s mixture, w h i l e s t i l l hot, over twelve quarts of good
oats, and mix until a l l grain is coated. A f u l l tablespoonful makes a
s i n g l e bait spot.
POISONED GRAIN HEADS:
Barley or milo heads may be treated with the strychnine paste used in
the poison oats formula, diluted with 3 pints of hot water. They should be
dipped into the hot paste and then allowed to d r i p for a short time and
dry. When gathering the heads, cut the stem 12 to 16 inches in length for
convenience in dipping and exposing.
95
POISONED SALT FORMULA:
One ounce of table salt ground together in a mortar w i t h 1/12 of an
ounce of powdered strychnine a l k a l o i d often gives good control, esp ecial ly
d u r i n g the green feed period. To prevent stock from taking it , the mixture
may be put i n to one inch holes bored into short blocks of wood. These can
be placed near feeding grounds or in spots where p i l e s of a l f a l f a may have
been placed to attract the rabbits.
LITERATURE CITED:
Eadie, W, Robert - (1954 ANIMAL CONTROL IN FIELD, FARM AND FOREST - The
McMilla n Co., New York.
.
H a s k e l l , Horace S. and Reynolds, Hudson G.-(1947) GROWTH, DEVELOPMENTAL
FOOD REQUIREMENTS AND BREEDING ACTIVITY OF THE CALIFORNIA JACK RABBIT Journal of Mammalogy Vol.28, No.2, pg. 129-136.
H i l d r e t h , A. C. and Brown, G. B. - (1955) REPELLENTS TO PROTECT TREES AND
SHRUBS FROM DAMAGE BY RABBITS - U. S. Dept. of Agriculture Technical
Bulletin No. 1134.
I n g l e s , Lloyd G. - (1954) MAMMALS OF CALIFORNIA AND ITS COASTAL WATERS Stanford U n i v e r s i t y Press, Stanford, C a l i f o r n i a .
McCabe, Robert; A. - (1957) FACTS ABOUT RABBITS - U n i v e r s i t y of Wisconsin
Circular 537.
O r r , Robert T. - (1940) THE RABBITS OF CALIFORNIA (Occasional Papers No. 19) C a l i f o r n i a Academy of Sciences, San Francisco.
Vorhies, Charles T. and Taylor, Walter P. - (1933) THE L I F E HISTORIES AND
ECOLOGY OF JACK RABBITS IN RELATION TO GRAZING IN ARIZONA - University
of Arizona, Technical Bulletin No. 49.
. CONTROLLING RABBITS - (1959) Branch of Predator and
Rodent Control, U. S. F i s h and W i l d l i f e Service.
_________________
. RABBITS IN RELATION TO CROPS - (1942) Conservation
B u l l e t i n No. I I , U. S. Fish and Wild 1ife Service.
_________________
96